The present invention relates to a device for optically inspecting surfaces.
German Published Patent Application No. 32 32 904 describes a device in which where a laser radiation is directed toward a surface to be inspected within a bore in a workpiece, and in which the radiation reflected by the surface is altered as a function of the surface properties. An input radiation is conducted toward a mirror by a central optical waveguide, the mirror deflecting the input radiation by approximately 90xc2x0 toward the wall of the bore. The radiation reflected by the surface is guided out of the bore, on one hand, by the central optical waveguide, and, on the other hand, by further optical waveguides concentrically arranged around the central optical waveguide. Between the central optical waveguide and the further optical waveguides, provision is made for an optical dead zone. Thus, the device enables in a simple manner a concurrent measurement both in the bright and the dark field of the radiation reflected by the surface.
An object of the present invention is to specify a device for optically inspecting surfaces which has a simple design. The device according to the present invention has an advantage that a first and at least a second surface can be inspected at the same time. Apart from the individual determination of measuring results, a comparative measurement between the two surfaces to be inspected is possible without having to move the device for that purpose.
According to the present invention, provision is made for a beam splitter to couple out, from an input radiation, a first measuring radiation directed toward the first surface to be inspected, and a second measuring radiation directed toward the second surface to be inspected. In the beam splitter, the measuring radiations reflected by the surfaces are brought together again to form an output radiation which is conducted toward a measuring device which measures the two measuring radiations separately. The two measuring radiations have different properties which enable a separate evaluation in the measuring device.
The device according to the present invention is particularly suited for inspecting surfaces in bores, especially, in blind-end bores. The simple design of the device according to the present invention enables the inspecting of surfaces in bores having a small bore diameter. A separate evaluation of the measuring radiations contained in the output radiation enables, for example, the determination of the straightness or the roundness of the bore. Since, moreover, the measuring results of both surfaces are available coincidently, it is possible to determine, for example, the alignment of the bore.
A first embodiment according to the present invention makes provision for different polarization planes as properties of the measuring radiations.
Preferably, the different polarization planes are achieved by designing the beam splitter as a polarization beam splitter. Suitable input radiation includes, for example, a nonpolarized or a circularly polarized radiation. Instead of the polarization beam splitter, it is also possible to use a conventional beam splitter, downstream of which polarization filters are arranged in the beam paths of the two measuring radiations, respectively.
One embodiment according to the present invention provides for already polarizing the input radiation in a predefined polarization plane. By changing the polarization plane, for example, by using a polarization rotator, it is possible to inspect the two surfaces consecutively. In this embodiment, the measuring device can be implemented in a particularly simple manner, since the output radiation corresponds to either the first or the second reflected measuring radiation. A signal which controls the polarization rotator assumes the association of the acquired signal with the respective reflected measuring radiation in the measuring device.
Another embodiment according to the present invention provides for the different properties of the measuring radiations to be selected using different wavelengths. The input radiation contains two portions of radiation having different wavelengths, wavelength-selective filters being arranged in the beam path of the first and of the second measuring radiation, respectively. Provided that the input radiation contains both portions of radiation coincidently, it is possible to measure the reflected measuring radiations simultaneously in the measuring device using appropriate wavelength-selective filters. Provided that the input radiation has sequentially different wavelengths, a measuring device is sufficient which measures the output radiation independently of the wavelength.
Another advantageous embodiment according to the present invention provides for the beam splitter to couple out the first measuring radiation at an angle of at least approximately 90xc2x0 with respect to the direction of the input radiation, and to let the second measuring radiation pass essentially without a change in direction.
A further advantageous embodiment according to the present invention provides for a beam deflector to be arranged in the beam path of the second measuring radiation so as to deflect the beam path in a different direction. Provided that the change in direction is at least approximately 90xc2x0, the two surfaces to be inspected can be located in one plane. Thus, it is possible to judge a bore at different bore depths at the same time.